did you draw a diagram? try drawing one and posting it, so the answer will become clear to you.

for question (a):

obviously (you'll see this from the diagram) ABC forms a triangle. all the angles of a triangle add up to 180 degrees. you are given two angles in the triangle. how would you find the third?

for question (b):

again, a diagram is important here. once you have a diagram, all you need to find the required angles is the Alternate Segment Theorem. see what it says here (it's a little more than half way down the page)